During photographic film camera manufacturing, it is common practice to test the operation of film advance, metering, and shutter mechanisms. With some cameras, each of these mechanisms can be tested by use of externally accessible camera features without film in the camera. This is often referred to as "dry-firing" the camera. U.S. Pat. No. 5,649,258 describes automated test equipment usable with an example of this type of camera. Other photographic film cameras cannot be dry fired because film winding and shutter mechanism setting must be accompanied by movement of a film driven preset member of the camera unit.
The term "camera unit" is used herein to refer to a completely or incompletely assembled camera. The term "preset member" is used herein to refer generically to a part of the camera that extends into the film plane and must be moved to meter from one film frame to the next. The preset member is positioned in alignment with film perforations and, during use, the preset member moves as the film advances and the perforations are pulled past the preset member. The preset member either by itself, or as part of a larger mechanism, meters the film during film advance, that is, limits film advancing so as to cause an appropriately sized and positioned frame of film to register with the exposure frame of the camera. Since the preset member contacts the film during metering, the configuration of preset member is largely dependent upon the number and type of perforations in the film and the motion of the preset member during film advance. Some cameras have preset members that are pawls having one or more teeth. The pawl pivots or retracts during film advance to allow the film to pass and then moves into the appropriate perforation as the film is metered. In some cases, the preset member acts indirectly by locking or unlocking a shutter mechanism. In other cases, the preset member must be moved to set or preactuate the shutter mechanism. An example of the latter is a sprocket that must be rotated to cock a shutter mechanism. With 35 mm film, the preset member is typically a rotatable sprocket wheel having multiple teeth, uniformly spaced apart in the same manner as the film perforations. The sprocket wheel is typically rotated once per film frame advance. APS film has two perforations per frame. Some APS film cameras have a sprocket wheel with 4 appropriately spaced teeth that rotates once per two frames of film advance. Other sprocket wheels, with one or more teeth, vary in a similar manner.
The inability to dry-fire cameras having film driven preset members has been viewed as a shortcoming from the viewpoint of in-store demonstrations of camera features and some cameras have been sold with "dummy" film cassettes that include a length of non-processable film, to permit repeated dry firing. U.S. Pat. No. 3,253,797 teaches a dummy Type 126 film cassette, in which non-processable film is advanced from one chamber to another of the dummy cassette to demonstrate camera operation. After the demonstration, the camera film advance mechanism is retracted and a spring within the dummy cassette automatically rewinds the non-processable film. U.S. Pat. No. 5,136,317 teaches a dummy 35 mm cassette used, not for dry firing; but rather magnetic head cleaning. U.S. Pat. No. 4,325,620 discloses use of a test cassette having a graduated non-processable filmstrip. These approaches have the shortcoming that the non-processable film is curled about the take-up spool and advance mechanism or spindle of the camera during the "dummy" operation, demonstrating, testing, or cleaning. The non-processable film must be rewound off the advance mechanism at the end of the dummy operation. This step takes time and, in manufacturing, might require additional equipment. Both increase manufacturing costs.
U.S. Pat. No. 3,899,245 discloses a testing device for cinematographic cameras, in which a test cassette has a loop of film bearing test images. A fiber optic cable extending through holes in the camera and cassette projects light through the film and lens to a screen.
In-store dry firing is not an issue for one-time use cameras, since they are sold preloaded with film; however, camera film advance and metering mechanism testing (also referred to herein as "wind" testing) and camera shutter mechanism testing (also referred to herein as "trip" testing) are commonly performed on one-time use cameras using 35 mm film or the like, by initially loading film with a portion of the trailer in the exposure frame of the camera. (One-time use cameras are commonly loaded with prewound film, which is then advanced back into the film cassette.) The shutter trigger is then tripped and the film is advanced to test the camera. Since the frame of film used for testing is part of the trailer, all regular film frames remain available to the user. This procedure is described in columns 1-2 of published European Patent Application EP 0 733 936 A1.
Reusable cameras using APS films can provide drop-in loading since the film is fully retained in the film canister and there is no leader to position during film loading. A lengthy leader is unnecessary and is not provided. This presents a problem for APS one-time use cameras. Wind and trip testing of a portion of the film in an APS one-time use camera would reduce the number of exposures available to the user. European Patent Application EP 0 733 936 A1 describes approaches to this problem. The shutter is charged by an appliance that is extended into the camera through a slot or is set by rotating a winding wheel that moves the film and sets the shutter independently of the film perforations. In both cases, the film is not advanced beyond a trailer portion of the film and the test exposure does not reduce the number of film frames available to the user. These approaches have the shortcomings that metering is not tested, and the operation of film advance and shutter mechanisms is tested in a different manner than the camera will be used. Japanese Patent Application publication JP 5-323517, filed Dec. 7, 1993, describes another approach. A shutter mechanism is set, before assembly with the remainder of a camera unit and film loading. This approach allows shutter testing, without film advance or metering. Japanese Patent Application Publication JP 7-13279, filed Jun. 23, 1993, describes a procedure for setting a shutter mechanism before assembly with the remainder of a camera unit. U.S. Pat. No. 3,003,229 describes a similar approach.
It would thus be desirable to provide camera wind and trip testing methods and apparatus for use with a camera unit including a film spindle and a film driven preset member, in which wind and trip can be tested without the use of a film cassette and without curling a non-processable strip about an advance mechanism.